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When Replacing A Light Fixture, What Do I Do With The Ground Wire?

February 25, 2007

Q: I’m trying to replace this old and ugly chandelier over my dining room table. I bought a light that I really like and I was told this would be a straight forward installation. I turned off the breaker and took down the old light. But when I got the light down, I noticed there were only 2 wires coming into the box and they are both black. I didn’t pay attention to how they were connected to the old light. So I asked a friend and he told me to get a magic wand voltage detector. I got one of these and I figured out which wire is the power and which is the neutral.

But there is not a ground anywhere in the box. The old light did not have a ground either. What do I connect the ground wire from my new light to? This above friend told me to connect it to the box. Another friend told me to connect it the the neutral and a third frien told me not to connect it to anything. I’m confused by three different answers. Thanks in advance for your help.

A: This is a common question we get all of the time and I was surprised to see I have not blogged about this yet.

DO NOT connect the ground wire to the neutral. This is very dangerous. The neutral is a current carrying conductor and the ground is not. By connecting the ground to the neutral, you will have current on everything metallic that is connected to this ground wire.

You usually can’t go wrong by attaching the ground wire to the metallic box with a green ground screw. However, if the box is not grounded this will do nothing.

If your wiring is installed in conduit or BX cable, your light box may be grounded. The way to determine this is to carefully test for a ground. This part is dangerous and if you are unsure of what you are doing or uncomfortable working with live electricity, I recommend hiring a licensed electrician. 

First, place a wirenut on the neutral conductor and bend it out of the way. Now place a wirenut on the power supply wire and go turn this circuit on. Next, wear a pair of leather gloves and get a voltage tester. Finally, wearing your leather gloves, remove the wirenut and check for voltage between the hot wire and the light box. If there is approximately 120 volts, your box is grounded.

Now just because you are wearing leather gloves, do not think you are superman and invinsible against live electricity. Leather gloves only provide a limited amount of insulation between you and the live conductor.

Make sure you turn off the power again to this circuit before continuing with your installation.

If you need further clarification or have more questions, please submit them in the comment section of this post.

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Comments

One Response to “When Replacing A Light Fixture, What Do I Do With The Ground Wire?”

  1. Bill on August 14th, 2007 9:55 am

    This question is a lot like a problem I’m experiencing, but the answer does not not address cases of knob and tube wiring. If installing a new light fixture on a K&T wired box, should the ground be ignored? Is such an installation appropriate for this system?

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